The Irminger Gyre: Circulation, convection, and interannual variability

• Published in: Deep Sea Research Part I: Oceanographic Research Papers
• Main Authors: Våge, Kjetil, Pickart, Robert S., Sarafanov, Artem, Knutsen, Øyvind, Mercier, Herlé, Lherminier, Pascale, Van Aken, Hendrik M., Meincke, Jens, Quadfasel, Detlef, Bacon, Sheldon
• Other Authors: Woods Hole Oceanographic Institution (WHOI), P.P. Shirshov Institute of Oceanology (SIO), Russian Academy of Sciences Moscow (RAS), SINTEF Ocean Space (SINTEF OCEAN), Stiftelsen for INdustriell og TEknisk Forskning Digital Trondheim (SINTEF Digital), Laboratoire de physique des océans (LPO), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Royal Netherlands Institute for Sea Research (NIOZ), Institut für Meereskunde Hamburg, Universität Hamburg (UHH), National Oceanography Centre Southampton (NOC), University of Southampton
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: Irminger Sea; Labrador Sea Water; Deep Western Boundary Current; Irminger Current; North Atlantic; Deep convection; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Labrador Sea
• Online Access: https://hal.archives-ouvertes.fr/hal-00650962; https://doi.org/10.1016/j.dsr.2011.03.001

International audience In this study 36 hydrographic transects occupied between 1991 and 2007 in the vicinity of the WOCE A1E/AR7E section are used to investigate various aspects of the Irminger Gyre, a narrow cyclonic recirculation in the southwest Irminger Sea. Vertical sections of absolute geostrophic velocity were constructed using satellite and shipboard velocity measurements, and analyzed in conjunction with the hydrographic data and meteorological fields. The Irminger Gyre is a weakly baroclinic feature with a mean transport of 6.8±1.9 Sv (View the MathML source). At mid-depth it contains water with the same properties as Labrador Sea Water (LSW). During the 17-year study period large changes occurred in the gyre and also within the boundary flow encircling the Irminger Sea. The gyre intensified and became more stratified, while the upper-layer circulation of the boundary current system weakened. The latter is consistent with the overall decline of the North Atlantic subpolar gyre reported earlier. However, the decline of the upper-ocean boundary currents was accompanied by an intensification of the circulation at deeper levels. The deep component of both the northward-flowing boundary current (the Irminger Current) and the southward-flowing boundary current (the Deep Western Boundary Current) strengthened. The increase in transport of the deep Irminger Current is due to the emergence of a second deep limb of the current, presumably due to a shift in pathways of the branches of the subpolar gyre. Using a volumetric water mass analysis it is argued that LSW was formed locally within the Irminger Gyre via deep convection in the early 1990s. In contrast, LSW appeared outside of the gyre in the eastern part of the Irminger Sea with a time lag of 2-3 years, consistent with transit from the Labrador Sea. Thus, our analysis clarifies the relative contributions of locally-versus remotely-formed LSW in the Irminger Sea.